Traumatic brain injury (TBI) is a major problem in the veteran population and there are no effective treatments proven to improve long-term recovery. In new preliminary data, we have found that the concentration of the cyclopentenone prostaglandin (CyPG) D12-prostaglandin J2 (D12-PGJ2) is increased in rat brain after TBI. CyPGs such as D12-PGJ2 are potent ligands of the PPARg nuclear receptor, and have been proposed to play an important role in resolution of inflammation and wound healing after injury and infection. CyPGs may also injure neurons by non-PPAR3-mediated effects including disruption of the ubiquitin proteasome pathway (UPP). In additional preliminary data, we have found that CyPGs bind to and inhibit the action of the key neuronal UPP enzyme, ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1) in neurons resulting in accumulation of ubiquitinated proteins and neuronal cell death. In these proposed studies, we will further characterize the production of and metabolism of CyPGs after TBI. We will also determine the role of PPARg activation and restoration of UCH-L1 activity in determining recovery after TBI and long term behavioral outcome. The following specific aims are proposed: 1. Characterize the time course of production of cyclopentenone prostaglandins and their metabolites after controlled cortical injury (CCI) in rats. 2. Test whether activation of the PPAR3 receptors reduces secondary injury and improves behavioral recovery after TBI. 3. Test whether restoring UCH-L1 activity by systemic treatment with a TAT-UCH-L1 fusion protein can prevent accumulation of Ub-proteins and improve behavioral outcome after TBI. TBI will be induced using the controlled cortical impact injury model in rats and mice. Concentrations of CyPGs will be measured in brain after TBI by quadrupole LC MS/MS using selective reaction monitoring of daughter ion fragments of the CyPG parent masses. Neutrophil migration will be quantified by measuring myleoperoxidase activity in brain tissue. The proteins, iNOS, TNFa, and MMP-9, which are known to be regulated by PPARg, will be measured by ELISA and used as downstream monitors of PPARg activation. Disruption of the UPP in brain after TBI will be determined by monitoring UCH-L1 activity and detecting accumulation of ubquitinated proteins by immunoblotting and immunohistochemistry. Behavioral outcome will be assessed using a working memory variation of the Morris Water Maze procedure assessed on post trauma days 14 through 20. These preliminary data represent the first report that CyPGs are present in brain after TBI. Activation of PPARg and restoration of lost UCH-L1 activity are new therapeutic approaches to TBI that could lead to novel therapies that could improve long term recovery and restoration of function after TBI.